﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.ApplicationModel;
using Windows.ApplicationModel.Activation;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.Phone.UI.Input;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Animation;
using Windows.UI.Xaml.Navigation;
using System.Threading.Tasks;
using System.Diagnostics;

// The Blank Application template is documented at http://go.microsoft.com/fwlink/?LinkId=391641

namespace VoiceSnap
{
    /// <summary>
    /// Provides application-specific behavior to supplement the default Application class.
    /// </summary>
    public sealed partial class App : Application
    {
        private TransitionCollection transitions;

        /// <summary>
        /// Initializes the singleton application object.  This is the first line of authored code
        /// executed, and as such is the logical equivalent of main() or WinMain().
        /// </summary>
        public App()
        {
            this.InitializeComponent();
            this.Suspending += this.OnSuspending;
            HardwareButtons.BackPressed += this.HardwareButtons_BackPressed;
        }

        /// <summary>
        /// This event wraps HardwareButtons.BackPressed to ensure that any pages that
        /// want to override the default behavior can subscribe to this event to potentially
        /// handle the back button press a different way (e.g. dismissing dialogs).
        /// </summary>
        public event EventHandler<BackPressedEventArgs> BackPressed;

        /// <summary>
        /// Invoked when the application is launched normally by the end user.  Other entry points
        /// will be used when the application is launched to open a specific file, to display
        /// search results, and so forth.
        /// </summary>
        /// <param name="e">Details about the launch request and process.</param>
        protected override void OnLaunched(LaunchActivatedEventArgs e)
        {
            if (CommonInitialize())
            {
                Frame rootFrame = Window.Current.Content as Frame;

                // When the navigation stack isn't restored navigate to the first page,
                // configuring the new page by passing required information as a navigation
                // parameter
                Debug.Assert(rootFrame.Navigate(typeof(ShowMe), e.Arguments), "Failed to create initial page");
            }

            // Ensure the current window is active
            Window.Current.Activate();

            // This is a great place to install Voice Commands!
            AppUtil.LoadVoiceCommandDefinition();
        }

        /// <summary>
        /// This function is called when an app is Voice activated
        /// </summary>
        /// <param name="args"></param>
        protected override void OnActivated(IActivatedEventArgs args)
        {
            CommonInitialize();

            Frame rootFrame = Window.Current.Content as Frame;

            // Decide which page to navigate to
            var vcArgs = args as VoiceCommandActivatedEventArgs;
            if (vcArgs != null)
            {
                IReadOnlyList<string> vcdTargetList;

                // Navigation Target attribute is optional for command definition in VCD.
                // If Navigation Target is not included in command definition, we launch default page e.g. in case of this app ShowMe.xaml
                Type navType = typeof(ShowMe);

                // For the voice command that is currently activating the application, try to navigate to the corresponding target page within the application.
                // This is the navigation target element specified for that voice command in VCD file.
                if (vcArgs.Result.SemanticInterpretation.Properties.TryGetValue("NavigationTarget", out vcdTargetList))
                {
                    // For simplicity, the navigation target specified in the VCD corresponds to a page type. Convert that page type
                    // into a namespace-qualified type here.
                    var vcdNav = Type.GetType(typeof(App).Namespace + "." + vcdTargetList.First());
                    navType = vcdNav == null ? navType : vcdNav;
                }

                Debug.Assert(rootFrame.Navigate(navType, args), "Failed to create initial page");

            }

            // Ensure the current window is active
            Window.Current.Activate();
        } 

        /// <summary>
        /// This method will perform Application initialization tasks as required.
        /// </summary>
        /// <returns>True: if initializing a first navigation, False otherwise</returns>
        private bool CommonInitialize()
        {
            bool appInitializationRequired = false;
            Frame rootFrame = Window.Current.Content as Frame;

            // Do not repeat app initialization when the Window already has content,
            // just ensure that the window is active
            if (rootFrame == null)
            {
                // Create a Frame to act as the navigation context and navigate to the first page
                rootFrame = new Frame();

                // Change this value to a cache size that is appropriate for your application
                rootFrame.CacheSize = 1;

                // Place the frame in the current Window
                Window.Current.Content = rootFrame;
            }

            if (rootFrame.Content == null)
            {
                // Removes the turnstile navigation for startup.
                if (rootFrame.ContentTransitions != null)
                {
                    this.transitions = new TransitionCollection();
                    foreach (var c in rootFrame.ContentTransitions)
                    {
                        this.transitions.Add(c);
                    }
                }

                rootFrame.ContentTransitions = null;
                rootFrame.Navigated += this.RootFrame_FirstNavigated;

                appInitializationRequired = true;
            }

            return appInitializationRequired;
        }

        /// <summary>
        /// Restores the content transitions after the app has launched.
        /// </summary>
        /// <param name="sender">The object where the handler is attached.</param>
        /// <param name="e">Details about the navigation event.</param>
        private void RootFrame_FirstNavigated(object sender, NavigationEventArgs e)
        {
            var rootFrame = sender as Frame;
            rootFrame.ContentTransitions = this.transitions ?? new TransitionCollection() { new NavigationThemeTransition() };
            rootFrame.Navigated -= this.RootFrame_FirstNavigated;
        }

        /// <summary>
        /// Handles the back button press and navigates through the history of the root frame.
        /// </summary>
        /// <param name="sender">The source of the event. <see cref="HardwareButtons"/></param>
        /// <param name="e">Details about the back button press.</param>
        private void HardwareButtons_BackPressed(object sender, BackPressedEventArgs e)
        {
            Frame frame = Window.Current.Content as Frame;
            if (frame == null)
            {
                return;
            }

            var handler = this.BackPressed;
            if (handler != null)
            {
                handler(sender, e);
            }

            if (frame.CanGoBack && !e.Handled)
            {
                frame.GoBack();
                e.Handled = true;
            }
        }

        /// <summary>
        /// Invoked when application execution is being suspended.  Application state is saved
        /// without knowing whether the application will be terminated or resumed with the contents
        /// of memory still intact.
        /// </summary>
        /// <param name="sender">The source of the suspend request.</param>
        /// <param name="e">Details about the suspend request.</param>
        private void OnSuspending(object sender, SuspendingEventArgs e)
        {
            var deferral = e.SuspendingOperation.GetDeferral();

            // Save application state and stop any background activity here.

            deferral.Complete();
        }
    }    
}